Current practice for fabricating metal mirrors is to machine the mirror from a single raw billet or forging. In one embodiment, the optical surfaces of an aluminum mirror could be machined as two-pieces, which are brazed together, and then mated with a thermal shrink fit hub. With such mirrors, it is challenging to properly install the hub into the mirror before a thermal equilibrium between the mating parts is achieved. A majority of larger diameter (e.g., greater than ten inches diameter) monolithic metal mirrors, when employed in military environments, require the use of adhesives to restrain against highly dynamic shear loads. Required fastener clamping loads, adequate to resist such shear forces, exceed the allowable bolt-up strain limits (few millionths of an inch) for the mirror's surface figure.
Achieving diffraction limited optical performance, from telescopes employing such mirrors, typically dictates mirror misalignments not exceed one ten thousandth of an inch. Achieving adequate load capacity to guarantee such alignment registration, for large mirrors exposed to shock loads, results in design, fabrication, and assembly challenges. For this application, the common usage of interference-fit fasteners, like pins, for restraining against shear loads is also problematic. Significant stress levels, generated with press-fit pins, propagate through materials generating strains. Unlike many typical machine parts, the optical performance of mirrors, subjected to strains greater than several millionths of an inch on their reflective surfaces, are significantly degraded. Thus, a need exists for a mirror mount assembly that is configured to provide precision registration for large diameter metal mirrors, during exposure to high shear loads (e.g., greater than 26 Gs), without stressing the optical surface of the mirror.